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Abstract

Gcs1 is an Arf GTPase-activating protein (Arf-GAP) that mediates Golgi-ER and post-Golgi vesicle transport in yeast. Here we show that the Snc1,2 v-SNAREs, which mediate endocytosis and exocytosis, interact physically and genetically with Gcs1. Moreover, Gcs1 and the Snc v-SNAREs co-localize to subcellular structures that correspond to the trans Golgi and endosomal compartments. Studies performed in vitro demonstrate that the Snc-Gcs1 interaction results in the efficient binding of recombinant Arf1Δ17N-Q71L to the v-SNARE and recruits purified coatomer. In contrast, the presence of Snc had no effect upon Gcs1 Arf-GAP activity in vitro, suggesting that v-SNARE binding does not attenuate Arf1 function. Disruption of both the SNC and GCS1 genes results in synthetic lethality, while over-expression of either SNC gene inhibits the growth of a distinct subset of COPI mutants. Finally, we show that GFP-Snc1 recycling to the trans Golgi is impaired in gcs1Δ cells. Together, these results suggest that Gcs1 facilitates the incorporation of the Snc v-SNAREs into COPI recycling vesicles and facilitates endosome-Golgi sorting in yeast.